Rokinon 8mm vs. 10mm vs. Sigma 8-16mm vs. Pentax 10-17mm Ultra-wide Showdown

Construction and Handling

In this section we scrutinize every aspect of the physical construction of these four lenses so you can appreciate exactly what each mix of metal, plastic, and glass entails - before ever putting your sandwich clamps on any of them.

Clicking on any of the images below will open an enlargement.

EDITORIAL NOTE: Unless otherwise specified, all the lens images on this page will follow the same arrangement. From left to right, they will be arrayed in the following order: Rokinon 10mm F2.8, Pentax DA 10-17mm Fisheye, Rokinon 8mm Fisheye, Sigma 8-16mm.

Front Element and Filters

The first thing to grab your attention is a shared attribute among the lot. The front element of these four lenses is very bulbous (especially the pair reaching 8mm), and as such, none feature any filter threads or engravings around the edge of the glass akin to some Pentax lenses:

For reference, here's an example of one of the more ubiquitous Pentax lenses with its name and filter size on the face of the lens:

Standing straight up and rotated to the side so the embedded hoods aren't blocking the view, you can really get an appreciation as to why embedded filter threads just aren't possible with these lenses due to the curvature of the glass in the front element:

Once again, the hoods are embedded. What this means is that they are permanently affixed to the lens body as part of its inherent construction. Thus, they cannot be removed. Unfortunately for those familiar with Pentax's Limited lenses—where some have embedded hoods that retract—"fixed" is very much the state of things here. Combine that with the lack of any filter threads and it quickly becomes tedious to mount filters to the front of the lens. We say "tedious" rather than "impossible" because while your circular XX mm filters aren't compatible, there are workarounds for those that are insistent. Some DIY ("Do-it-Yourself") solutions exist as well as professionally regarded filter system manufacturers (Cokin, Lee, Formatt Hitech, Fotodiox, etc.), where they have created filter holders specifically designed for such lenses. But again, they are tedious to use, as the below product image from Cokin demonstrates:

If you notice above, the generic camera and kit lens are connecting to an adapter ring. Again, what makes these four lenses (or any other without filter threads) in particular so cumbersome is that the adapter ring is replaced by a shroud that fits around the outside of the lens since there's no filter threading to screw an adapter ring onto. Combine that with the exceptionally wide field of view—which requires larger rectangular filters—and that awareness (slightly) lessens the shock of just how much Hitech Formatt's Lucroit system dwarfs the Sigma 8-16:

Even after coming to grips with carrying all the extra components and the time and deliberation needed to set everything up and then break it down, more pressing of a consideration for most photographers is the sheer cost. Filter systems—which comprise of the filter holder, the lens attachment, and various rectangular slide-in filters—tend to be very unfriendly to your wallet. In fact, such a kit often costs more than any of the four lenses considered in this review!

Front Lens Caps

As for the front lens caps, they shroud the entire front of the lens, including the lens hoods:

With the front caps unattached and rotated on their sides, it becomes clear just how large and unwieldy they are, save for the Pentax fisheye:

The Sigma 8-16 on the far right has a slightly unique cap due to being comprised of two parts. First, the cylindrical shroud that fits around the hood and then a regular pinch-type cap (72mm) you would find with any lens with a typical filter-ready front element. Because of how those pinch-type caps attach (by having teeth fit into the grooves of filter threading), that would mean the inside of the Sigma's shroud can accept standard circular filters. While this is technically true, it's ultimately a failed attempt because of how the shroud affects the field of view enabled by the petal shape of the embedded hood. The below table shows this clearly, with depictions at 8mm, 12mm, and 16mm:

	Without Shroud	With Shroud
8mm
12mm
16mm

Frankly, we have no idea why Sigma opted for this style of lens cap (their full frame 12-24mm UWA rectilinear zoom also features the same two-piece design). We would have preferred if they just made it one solid item like the others, however it doesn't detract from the use or quality of the lens in anyway. Just an odd and peculiar detail on behalf of the engineers is all.

From a purely aesthetic point of view (and not taking size into account), the Pentax has by far the nicest quality cap as it is entirely made of metal whereas the others are made of plastic. Because of how the Rokinon hoods aren't perfectly secure and tight when attached (there's a minor amount of wobble if you look for it), they lack the refined feel embodied by the two zooms.

Front Element Cleaning

Normally this is a closing comment in the above section, however we'd like to deliberately point out two observations regarding cleaning the lenses' glass (as some accidental finger prints may have appeared on the front lenses during our time with these optics).

First, while using a lenspen to clean the front objective, the lack of Pentax's Super Protect coating became immediately apparent. Hard to explain in words, it was merely a difference in "smoothness" between the SP coated lens (the Pentax fisheye) and the other three when rubbing the felt-tipped cleaning implement across them. On the Pentax lenses, the pen seemed to just smoothly glide across while the other three (the Rokinon's especially) seemed to exhibit a lot more friction, "sticking" a bit more. In fact, we were consistently able to get the lens pen to squeak! 

At the end of the day, it's not a huge issue and won't have a direct impact on the lens' image quality output, but it was a difference we immediately noticed. We first became attuned to this phenomenon during our in-depth review of the Sigma 18-35 F1.8 HSM "Art" lens. We suspect that should you be in inclement conditions (lack of weather sealing on any of these lenses aside), the Pentax should be a bit less prone to flecks of dust or small water droplets sticking to the glass thanks to the Super Protect treatment.

Much more of an inconvenience than any friction was the physical construction of the Sigma zoom and how it made it extremely difficult to reach all parts of the glass thanks to the embedded hood's very narrow profile:

Reversed Lens Hood for Storage

So remember how we just went on with that long diatribe with lots of sample photos and explanations of how the lens hoods are permanently attached? Well we lied. Sort of... 

The Rokinon 8mm Fisheye that we have for this review is the Mark II of this lens, which you can see in the above image to the right of "FISH-EYE CS II," with a better close-up below:

Both versions share the same optics and general body design except for two modifications. First, the lens has now been coated with proprietary nano coatings (UMC for Ultra Multi Coating) and the lens hood has been made removable. While an APS-C lens, the company had learned that many users were putting the 8mm prime on full frame cameras and then shaving the lens hood away to increase the field of view before the hood's vignetting took significant effect. 

As such, we were curious if the lens hood could be reversed in order to make the overall package a bit more compact when in storage/transport in the manner most lenses are able to do:

So while it does in fact mount reversed, to include very securely clicking in place, our excitement quickly dissipated when we realized how this fisheye's cap attaches. In the same manner as a regular lens cap, it has teeth that latch onto the inside of the rim's threading, which is visible above left with the lens hood attached properly. This is not in the same manner as the Pentax and Sigma lenses whose lens caps are precisely machined to just fit around the hood and stay affixed due to friction and a thin coat of microfiber.

Especially now with the lens hood off, we wanted to take a minute to re-emphasize why not including circular filter threads beyond the front glass element is a decision not taken lightly by the optical engineers. The inherent nature of ultra wide angle lenses makes it very prohibitive, and the above image portrays exactly why.

Anyway, in the below image, you can see how the cap fits completely over the hood and clasps down on the inside threading of the petal hood:

And a closer inspection of the clasp mechanism, which is the design also shared by the same manufacturer's 10mm prime:

Additionally, one other benefit of the ability to remove the lens hood eliminates the issue the Sigma zoom experiences where a lens pen can't reach certain areas:

Lens Body

As for the lens bodies themselves, they are all well built and enjoy tight tolerances, even if their makers chose different finishes:

On the Sigma you can see a switch to the bottom left of its profile. It's the only one of this group with such a feature and deals with enabling/disabling the in-lens focus motor.

The backside of these optics' lens barrels look as such:

Size Compared to Similar Lenses

Each of these lenses, whether prime or zoom, is an extremely niche and specialty lens rather than a standard/walkaround zoom or a "Nifty Fifty." What this means for the average photographer is that each one is a piece of kit that has to be deliberately considered whether or not to be thrown in the camera bag. To give greater context as to the size of these lenses and not just compared against each other, the Sigma 17-50 F2.8 premium standard zoom and the Sigma 85mm F1.4 have been added to the left and right flanks, respectively. Additionally, the animated .gif shows what difference the removable hoods make when possible:

It becomes very clear just how diminutive the Pentax zoom is, especially once the front caps vie for space in the camera bag. For those that do not have any of these lenses, the DA 10-17mm is the same size as the DA 18-55 kit lenses without the hood attached, albeit with much more heft (320g/11oz vs 230g/8oz, respectively).

Zooming and Barrel Extension

For this portion of our physical examination, we omitted the two primes for obvious reasons. Left with the Pentax and Sigma zooms, we found that they zoom in different manners. The Sigma lens was rotated off-center so the bulbous front element could be seen from behind the lens hood while simultaneously being able to view the focal length markings along the zoom ring:

The Pentax DA 10-17 exhibits typical zooming behavior, where its physical size extends as the focal length changes (regardless of how minor that extension may be). This is in contrast to an internal zoom where the lens' physical size is constant regardless of the focal length. The rectilinear lens on the right, however, is a bit of a hybrid. It's clear that the front element protrudes and retracts like the Pentax, however the embedded lens hood's position remains unchanged, and thus the overall size of the lens as well.

Internal Focus and Focus Distance Scale

Every one of the four lenses features an internal focus mechanism, which means that unlike the zooming behaviors exhibited above, there is absolutely no change in dimensions of these lenses while focusing. As the lenses vary between their minimum focus distances (MFD) and infinity, the lens elements are shifted back and forth inside the lens.

The lenses do, however, feature focus distance scales that take the guesswork out of figuring how near or far away your lens is focused. This is especially helpful on the all-manual focus lenses such as the two primes. With the exception the Sigma 8-16mm, the rest have the markings emblazoned on the outer shell of the lens. That exception features the more premium focus window, where the scale is actually on the inside of the lens body and encased behind a transparent shield.

Rokinon 10mm	Pentax DA 10-17mm Fisheye
Rokinon 8mm Fisheye	Sigma 8-16mm

Regardless of the implementation—laser-etched or through a window—both USA Standard and Metric units are provided. And finally, the Rokinon 10mm F2.8 takes it one step further and implements a Depth of Field (DOF) scale as well, which helps with determining the near and far distances within the plane of focus, per aperture, before taking the shot.

With the exception of macro lenses and some dedicated portrait lenses, both of which tend to exhibit very long focus "throws" (the term for how far you can turn the focus ring between the MFD and infinity), internal focus is no longer the mark of premium lens as they are becoming the defacto industry standard. Nonetheless, Pentax still removes any uncertainty by indicating such a feature in its official lens naming convention. Aptly enough, the two letter acronym is placed within brackets:

smc Pentax-DA 10-17mm F3.5-4.5 Fish-Eye ED [IF]

Lens Mount and Aperture Ring

The lens mounts of all four lenses are high grade metal rather than the plastic of cheaper, less durable consumer lenses. Despite only two of the four featuring autofocus, the entire lot have electrical contacts that pair with the female portion of the lens mount on Pentax DSLR's in order to provide some form of automation:

The reason we chose the wording "some form" to describe the level of automation is because all three brands' lenses (the specific lenses compared here) differ, which are explained in the table below:

We'll discuss the differences in the focusing mechanisms later on in this review, however the aperture automation is something we'd like to quickly highlight as it pertains to the Rokinon lenses. As a third-party lens manufacturer (just like Sigma), the lenses they make are available in a variety of mounts. What's particularly unique about Rokinon lenses is that while they are predominantly "manual-everything," they have long made an exception for Pentax (and now recently Nikon) where their lenses are equipped with the necessary contacts for exposure control via the camera body (rather than solely from the aperture ring) and the recording of complete EXIF data.

Here you can see the aperture rings of the two Rokinon lenses sporting an additional notch: the A position:

As such, these lenses are far more user-friendly on Pentax DSLR's. They can not only have their settings changed quicker during fast-paced events (weddings, anyone?), they are also compatible with other automated accessories such as P-TTL flashes that meter for accurate flash exposure through the lens.

Variable Aperture Chart

It's been mentioned that the two zooms are variable aperture lenses, which simply means the maximum aperture varies based on the focal length (which is the opposite of a constant aperture zoom). In order to make it easier to visually grasp the exact aperture range of these zooms, namely where each maximum and minimum aperture lies along the entirety of the focal length range, we've created the following diagram for you. Above the axis lie the maximum apertures, with the minimum possible openings underneath:

Verdict

All of the lenses are very well built and do not experience any unsettling rattling, shaking, looseness of components, etc. While they all have their own quirks and finishing touches as placed upon them by whatever manufacturer conceived them, they are all excellent in their own right. Of course, we lament the lack of weather sealing or the ability to natively accept filters in any of these ultra wide angle lenses, however that does not bring about any sense of "cheapness" when handling them.

One thing we feel compelled to note is that there are many reports that the Rokinons (and its Samyang, Bower, etc. kin) require calibration of the manual focus ring. What this entails is actually a minor "surgery" to realign the focus ring to have the infinity marker on the distance scale to match the lens' actual infinity focus setting. While variations in build quality do exist, as with any product, we wanted to say that after years of ownership by our reviewer as well as using different samples loaned to us for this review, we have never experienced this phenomenon with any Rokinon lens.

For a general overview of these lenses' optical qualities, move along to the next page.